there's a section:
USCIS Service Centers
If you contacted the National Customer Service Center with a case-related inquiry and more than 30 days have passed and you have not received a response, you may email the appropriate USCIS Service Center with your inquiry:
California Service Center: csc-ncsc-followup@dhs.gov
Vermont Service Center: vsc.ncscfollowup@dhs.gov
Nebraska Service Center: ncscfollowup.nsc@dhs.gov
Texas Service Center: tsc.ncscfollowup@dhs.gov
If you do not receive a response within 21 days of contacting the Service Center, you may contact the USCIS Headquarters Office of Service Center Operations by email at SCOPSSCATA@dhs.gov.
I think everyone can contact them after 21 days contacting ncsfollowup if there's no response.